Percussive tool



y Y Patented Apr. 29,1930

i GEORGE vn. erLMAN, ornati/rom, MASSACHUSETTS Appucaiion mea March 5, 192i, Serial 110.449,667, Renewed september 12,1929.

l ",My invention'relates to fluid pressure operated percussive'tools" and particularly but not exclusively to hammer rock drills;

' Myl invention will be best understood-from the accompanying 4drawings and following lde'scriptionof specific embodimentf'of my invention selected for illustrative purposes, while .the scope of my'invention will'be particularly pointed out in the appended claims. lo Y Inthe drawings: l v

Fligure lis a longitudinal section of a plug ril; Y l 2@ I: Figure`2 is a section'on the line 2-v-2 of Figure 1; and l5 Figure 2 with parts broken away and' showing the'piston at the end of'its stroke opposite that shown'byFig. 1. 'f A vThe submitted' .embodiment of my inven- V tioncomprises a cylinder in which is reciprocablymounted a ,hammerl partingpercusSion-to a drill steel 1 carried at rtheforward end ofthe cylinder, while at the rearward 'end ofthe cylinder I vprovide v av handle 2-for supporting the machine. Y

'The cylinder comprises a forward member 3 and a rearward-member 4, these members `respectively having formed therein ajforward bore'5 and asmaller rearward bore 6 communicating with the forwardfbore. The piston is provided with a head 7 fitting the forward bore and a shank yQfittingthe rearward bore while extendingforwardly from the head is'the hammer bar y10fornf'1ed to fit the reduced diameter portion 11 of the cylinder. The shank is provided with a'reduced diameter portion 12 near its juncturel with the l head and in a manner hereinafter Vdescribed the shank controls the admission of motive fluid to opposite sidesof the head.

rlhe bore 5 is provided with a portion of enlarged diameter 13 at its rearward end for receiving the forward portion 15 of the mem-- ber 4, the latter being provided withy a flange 1T forming a shoulder abutting the rearward end face'19 of the member 3. lRearwardly of the cylinder member 4 is located a head block' drilled through the wallof said member. Intermediate these grooves 'I' provide the radial Y passage 'wliich intersects the bore 6 and is 21 which is provided with a'sleeve 23 surrounding the end of the cylinder, the sleeve 5 being 'provided withinterior screw threads Figure`3- s a section `on the line 3-,3 of Y piston for imi moves the pressure of his hand from the han- `posit-ion illustrated by ward cylinder 'memberas indicated at 25 to fholdktlie vparts in assembled relation. A

Thehandle "member 2'is provided with a sleeve 29, slidably, mounted on the head block andis heldin position by theair hose nipple 31 which extends throughitheslot 33 formed in the sleeve and is threaded into the socket i '35 ofthe head block.' rlhroughthe head block is formed 'an axial boreV 37 which receives the tubular cushionl plug 39,.V SlidablyI mounted in the cushionplug is a cylindrical throttleV valve 41V provided with" a reduced diameter 'portion 43 adapted when thevalve is in its forward positionuasillustrated by Fig. 1'to establish communicationv between the .intake passage 45 and a passage l47 in communicationV with the annular groove 49v formed in the` surface of the head block abutting the rearward-'endof the cylinder member 4. Y The .aXialboreof thehead block receivingtheV ycushion plugis enlarged at its forward end to provide a ychamber 51for receiving the headr53`of the plug. .This chamber placed in constant communication withtheglive air supply by means of a passage 55 formalin taining a constant pressure against thev forward surface of the plug and throttle valve. From V*this .it follows when the operator re dle,the air in the chamber' 51 will move the throttle valve and handle rearwardly and interrupt communication between'the passages-45 and fromv reciprocating. With the handlein the Fig. 1, the air in the 4'? 'and thus stop thehamm'er Y chamber 51 acting on the head of the cushion plug and the forward end of the throttle I,

valve Vabsorbs the rearward vibration and thus prevents the same from being transmit-v ted tothe hand of the operator. v 1

' The bore 6 of the rearward cylinder member isenlarged at 57 and ..59 to form spaced annular grooves or chambers whichare placed iny communication with leach other and with `the annular groove 4 9 "of the head block by means of oneor more intersecting passages 61 in communication with the ports 65 of one Y, mitting escape of eXhaustair to theiatmosphere, the flange 17 is cut away at 75 to permit the air to pass into vthe interior of the .sleeve 23 whence it finds its way to the ati mosphere through one or more passages V77 Y and 79.

The forwardY end of the cylinder member 3 I' provide lwith a chuck 81 which receives theShaIik of the drill steel, the latter being struck by the hammer bar 1()l of the piston at the end of the forward stroke. The hammer bar'l fits the forward bore 11 of theV cylinder in a fluid tight manner but is of such length that when the Vpiston moves rearwardly, the

hammer bar withdraws from this portion and places the interior ef the bore 5 in communication with the atmosphere byV way of the chamber 8 9 and passage 91. Y y

When the Diten is in the position shown bylig. 1 air is admitted to the forward end of the bore 5 in front of the head 7 of the piston by wayof the passage 61, the annular grooves 57 and 59, the bore 6 and the yports and passages 63, 65, 67 and 69. At this time the rearward end of the bore 5 is connected to the atmosphere by way of the port 7 3, the passage 71 and ports 77 and 79 and under these conditions'the piston moves rearward ly. After the piston moves rearwardly far enough to close the passage, 63, the supply of vmotive iuid to the forward end of the cylin-v der is cut off to trap motive fluid in said forward endk which trapped fluid. works eX pansively until it kis released by the. head 7 Overrunning the exhaust port 73 and by the hammer bar withdrawing from the portion 11. `Vlfhen the'shank moves rearwardly past the groove 57, live air is trapped in the eX- treme rearward end of the bore 6 which acts to Vcushion the hammer and to increase the energy imparted to the piston during its forward stroke. y

When the piston has moved rearwardly to the position illustrated 'by F ig. 3, the air 'which isV constantly' supplied the annular Vgroove 59 is admittedy to the rearward side ofthe head 7 by way cf the reduced diameter portionof lthe piston,`which, aided by the continuous pressure on the rearward face of the shank., causes the pistonto move forward- Y 1y., vllirinf.; the forward' stroke, the air in trent et the` head 7` exhausts through'the passages 91 and 71 to the atmosphere as heretofore described.

'lo improve the action of the hammer 1 provide a reservoir chamber in the form of one or more drill holes 93 in the wall of the forwardrcylinder member' and in constant commimication with the annular groove 59 byA way of one or more passages 95. The purpose of the reservoir chamber is to make available a large volume of air for preventward cylinder chamber, these expansion chambers like the return passages 67 and reservoirs 93being drilled through the wall of the forward cylinder member and closed by the flange 17. Theexpansion chambers communicate with the bore 3 at a point slightly forward of the :rearwardend of the .Stroke of the head 5 by means of ports 99.

It will be borne in mind that a piston of Vthe type shown reciprocates about eighteen hundred times per minute, in other words, starting with the piston in the position shown by Fig.v 3, it moves forward and strikes a blow and returns to this position thirty times ineach second. It has been estimated that the'greatest portion of the time necessary for a hammer piston to move forward, strike its blow,return and again start forward is consumed in reversing the piston at the end of, its,V rearward stroke and for this reason it is of advantage not only to keep up the mean effective pressure by means of eXpansion chambers but to so form them that they will aid the piston in its reversal. With the present invention, after thel piston closes the exhaust port 78 on its rearward stroke, the back pressure is relieved 1by causing the residual amount of air between the head 7 and the rearward end of the bore 5 to be cempressed into the expansion. chambers and the decrease in back pressure so caused allows the piston to move rearwardly more rapidly than would otherwise Ybe the case. When the reduced portion 12 of the piston establishes communication between theV annular groove 59 and the rearward end of the large bore of the cylinder during the rearward movement of the piston, the motive fluid admitted into the bore vflows into the expansion chamber 97 during the time the port 99 is open but owing to the speed at which the piston is moving not enough is admitted to bring the pressure up to that of the line before the head closes the port 99 by its continued rearward mevement. After the port 99 is closed, the head 7 of the piston is exposed to air at line pressure, which is more effective to quickly stop and reverse the piston than if the expansion chamber at llO this time 'were open, because undersuch condit-ions, the air would iir'st haveto illfup the expansion chamber before linea pressure -not limited and thatextensive deviations from the same and appoint of cut-off prior would vbe available. Y

Although I have described one specific -embodiment of my invention for illustrative purposes, it i's to thereby to its particu/lar details may be made without departing Vfrom the spirit of my invention. i Clai'ins: "Y

y l. In a percussive tool, a cylinder 'and a piston presenting'opposed p res'si'irefsurfaces, means providing a chamber communicating with said cylinder adjacentits pressure surface and Vadapted to be closed from communication with said cylinder bysaid 'pistonat' the end of its stroke, and' means providingY for prea'dmission of motive iiuid between said opposed surfaces before closure of said chamber and for cutting off of motive fluid after said chamber is again opened.v

2. In a percussive tool, a cylinder and a pis-l ton presenting opposed pressure surfaces,

ymeans providing a chamber communicating withsaid cylinder adjacent its pressure surface and adapted to be'closed from commuiiicaticn with said cylinder by said piston at the end of its stroke, an exhaust conduit for the space between said surfaces, means for interrupting the flow through said exhaust conduit, andmeans other thansaid chamber for admitting motive iiuidbetween said sur-` faces after closure of rsaid-conduit and before *the closure of said chamber and for continuing such admissionafter Vclosure of said chamber.- f Y I c 3. In a percussive tool, a cylinder and a piston presenting opposed pressure surfaces,

means providing va chamber communicatingV with said cylinder adjacent its pressure surface and' adapted to be closed from communication withsaid cylinder by said piston at theend of its stroke, exhaust andadmission means for the space between said-opposed surfaces, means co'ntrolling said` admissionand exhaust means andproviding apoint of admission subsequent to the point Ofcompression and prior tothe closure of said chamber tothe. point of release and subsequent to the reopening of said chamber. lI y Y Y f 4;. In a percussive tool, aV cylinder having a forward chamber and a rearward chamber of smaller diameter than said forwardchamber, a piston having a head fitting said forward chamber and a shank liavinga reduced` portion adjacent its forward end fitting said rearward chamber, areservoir chamber opening into said forward chamber at such a position that said head closes ycommunication between said reservoir chamber and' said forward chamber at the rearward end of the travel of said head, and a pressure port comvberby said reduced portion at jend of the piston stroke.

5. In a percussive tool', a cylinder, a pistonY be understood that VI am n providing fber whenfsaid pistonis'at one end stroke,` valveless Vadmission means providing municating with the forward portion of said rearward chamber and positioned to beplaced in' communication with said rforward chamfor preadmission to said end of said cylinder chamf of its therearward whereby said chamber ischarged @with -live f ymotive fluid for 'storage thereinv duringy the preadmission and admissionperiod to said end of said cylinder and such stored motive lfluid is supplied to said end offsaid cylinder during the expansion period Vat said end.,V v

j 6. In a percussivetool, a cylinder having a-forward chamber and arr rearward lchamber soV of smaller diameter than said forward chaml ber, a piston having a head fitting said forward'cha'mber and a shank having a reduced portion adjacent its forward end lfitting said rearward chamber, a chamber formed inthe body of said cylinder and openingfinto said forward. chamber thro-ugli -a Yport positioned to be closed ward end of its stroke, means for exhausting the yrearward end of said forward chamber ywhen saidrhead is at theforward portion of its stroke, and portsand passages controlled by said reduced portion of said shank forjadvmitting motive said forward fluid to the rearward'end ,of hamber--during the rearward stroke after vcessation of said exhaust and before said -port is closed by said head and for continuing said admission after vsaid, head n 'closes said port.- f

n tool, -the combination with a cylinderreceiving a reciprocato'ry-piston and said piston having a pressure sur-face 7 .In a percussive by said head when at the rear'- which in conjunction with a pressure'surface Y of said cylinder formsanexpansible`- chamber, of means for alternately admitting motive fluid to and exhausting it from said ex- "pan'sible chamber, a reservoir chamber communicating with said expansible chamber at such a position that communication between the two is interrupted by said piston when said pressure surface of said piston approaches its position corresponding to maximum contraction of vsaid chamber, andmeans for admitting live fmotive fluid'to'said expansible chamber when said'pisto'n is at its j position corresponding to maximum contraction 'of said expansible chamber.

8. In a percuss'ive tool, the combination with a cylinder receiving `a reciprocatory piston andsaid piston havingY aY pressure surface which in conjunction with a Apressure surface of said cylinder forms an expansible chairmen-of means for alternatelya'dmitting motive fiuidto and exhausting'it from said eXpansi-ble chamber, a reservoir chamber communicating with said expansible chamber at such a position that communication between the two is-interrupted by said piston when said pressure surface of said piston approaches its position corresponding to maximum contraction of said chamber, and said means for admitting and exhaust-ing motive iuid providing for preadmission and compression for the fluid cycle for said expansivble chamber while said reservoir chamber is in 'communicationV with said expansible chamber.

9. .In a percussive tool, a cylinder, al piston in said cylinder forming in conjunction with said cylinder anexpansible chamber, means for', alternately admitting` and exhausting motive fluid to said chamber, reservoir means for relieving the eects of pressure opposing contraction of said chamber, said means being inoperative when said piston reaches the position in which it reverses its direction of reciprocation, and means for admitting live inotive fluid to ysaid expansible chamber for reversing the direction of reciprocation of said piston before said first named means is rendered inoperative. Y Y

lO. In a percussive tool, a cylinder, a piston reciprocably mounted in said cylinder, an admission port, said cylinder having formed Vtherein a reservoir communicating solely with said port,.and means responsive to motion of said piston for distributing the fluid n from said port for causing the piston to reciprocate. l Y

1l.In a `percussive tool, a cylinder, apiston reciprocably 'mounted in said cylinder, said piston having opposed pressure surfaces, means providing an annular chamber surrounding an intermediate portion of said piston,means for conducting motive fluid to said chamber, another chamber formed in said cylinder and communicating solely with said annular chamber, and means responsive to motion of said piston for distributing the fluid from said last named annular chamber for action alternately against the respective surfaces of said opposed surfaces for causing said piston to reciprocate.

l2. In a percussive tool, a cylinder having a larger chamber and smaller chamber, a piston having a head fitting said larger chamber and a shank fitting said smaller chamber, a live air admission port opening through the wall of said cylinder into said smaller chamber and at the end thereof adjacent said larger chamber, means affordingl a reservoir communicating solely with said port, and means for admitting fluid by way of said .port to said larger chamber.

13. In a percussive tool, a cylinder having a forward chamber anda smaller rearward chamber, a piston having a head fitting `said a forwardchamber and a shank having a reduced portion near its juncture with said head fitting' said rearward chamber, an annular groove formed in the wall of said rearward chamber at the forward end thereof, means establishing uninterrupted communication between said groove and a source of motive fluid supply, and means aording a reservoir communicating solely with said groove.

le. In a percussive tool, a cylinder having a forward chamber and a smaller rearward chamber, a piston having a head tting said forward chamber and shank i fitting said smaller chamber, a pair of spaced annular grooves formed in the interior surface of the wall of the smaller chamber, a passage formed in theV wall of the cylinder and intersecting Said grooves, means for connecting a source of motive fluid to said passage, and a passage opening into said rearward chamber between said grooves and being controlled by said shank for admitting motive fluid by way of both annular grooves tothe forward end of said larger chamber.

l5. In a percussive tool, a cylinder having a forward chamber and a smaller rearward chamber, a piston having a head fitting said forward chamber and shank having a reduced portion adjacent its forward end fitting said smaller chamber, a pair of spaced annular grooves formed in the interior surface of the wall of the smaller chamber, both annular grooves being overrun by said shank when said piston is at the forward portion of its stroke, a passage formed in the wall of the cylinder and intersecting said grooves, means for connecting a source of motive Huid to said passage, a passage leading from an intermediate portion of said smaller chamber to the forward end of said forward chamber, whereby the end of said shank may cause admission of motive fluid by way of both annular grooves to one side of said head and said reduced portion of said shank may cause admission of motive `liuid to the opposite side of said heady by way of one annular groove.

16. In a percussive tool, a cylinder having a forward bore and a smaller rearward bore, a piston having a head fitting said forward bore and a shank having a reduced portion near its forward end fitting said smaller bore, a passage for connection to a source of motive fluid supply and having a port opening into the forward endfof said smaller bore, conduit means for admitting motive fluid to the forward end of said forward bore and having a port opening into an intermediate p0rtion of said smaller bore, and said ports being so disposed whereby they are placed in communication by said shank at the end of the forward stroke for conducting motive fluid to the forward end of said forward bore and such communication is interrupted by said shank at the end of the rearward stroke' and whereby the first named port is placed by the reduced portion of said shank in communication with the rearwardend of having a bore and a'longitudinally extending JFluid receiving passage formed in the wall thereof and opening through its end surface, a second cylinder member having a bore and received by thebore of said rst named member, a flange carried by said second cylindery member closing saidy passage, a passage in said second cylinder member forwardly of said flange placing the bore of said secondy cylinder member in communication with said longitudinally extendingpassage, a piston in I .Y

saidv cylinder, and means including said pasl sages for reciprocatingsaid piston.y

18. In a percussive tool, a cylinder member having a bore and a longitudinally extended fluid receiving passage formed in the wall thereof land opening through its end surface, a second cylinder member having a bore yand received by the bore of said first named member, a vflange carried by saidsecondcylvinder member closing said passage, a piston j f vhaving portions fittingsaid bores, and'means Vfor reciprocating said piston including a:`

port controlled byfsaid piston for admitting Vfluid to said passage;V

Y 19. In a percussive tool, acylinder member having a bore anda passage opening through its'end surface, said passage having ,ports v communicating withlsaid bore lat opposite ends thereof, a second cylinder member hav- Y ing a bore and a shoulder and being inserted in the open end lofsaid first named cylinder member whereby said shoulder closes the end of said passage, saidl second member having a passage for establishing communication between its bore and one of the ports of the first named passage, and a piston tting said bores and opening and closing said second passage in its reciprocations.

` In testimony whereof, I have signed my name to this speciicatiomV I GEORGE H. GILMAN. 

